In a one-sort (or few-shot) challenge environment where everyone is attempting the same thing I would create a party much different then for an ongoing campaign, likely with a gimmick. Such as an all stealth party, each equipped with wings of flying (5*400gp) with the goal of bypassing as many encounters as possible.
Off the top of my head: Rogue, Bard, Druid, Barbarian, Bladesinger
Was originally going to do monk but the rules are punitive to short rest classes, which normally have last night's long rest + 2 short rests for 6-8 encounters (avg 2.33 encounters per rest) vs. this which (4 encounters per rest) - almost double. It also makes me worry about druid, so can't go ones that are powered by wildshapes, and bardic inspiration recharge.
Elven Rogue - Arcane Trickster. Traps, locks, best stealth, pickpockets, investigation. Archer, elven archery, Steady Aim from Tasha's to get advantage every round for their one attack. Alternately could go soul knife for telepathy in the party, but then move investigation to the bladesinger and they need to work together on traps and such. Noble background - both to get access to people with feature, and to get out of trouble if caught.
Changeling Bard - Lore, Eloquence or Glamour. Party face, stealth. Friends cantrip, to be used wearing other people's faces and leaving before it ends, so they get angry at the wrong people.
Satyr Druid - stealthy with either unobtrusive wildshape forms and boosting everyone with pass without trace. Perception, insight, wilderness/nature. Not a moon druid. Goodberries to get people up from unconscious after battle. Outlander background. Satyr for magic resistance. Healing - activating an already cast Call Lightning does not count as casting so can use a healing word or other bonus action spell in the same round.
Metallic Dragonborn Barbarian - barbarian, able to hold hold the line. Ancestors likely. Unsure of skill focus, see what's missing / could use double up on. STR for challenges that need it, DEX for AC and stealth, CON for HPs and unarmored AC. Fizban's dragonborn for being able to breath as one attack in an Attack action, metallic for the nifty other breath types. (Originally was thinking this was the Satyr, could work as well.)
Halfling (Mark of Healing) Bladesinger - needed a wizard, artificer, or 2nd rogue for INT based challenges. Bladesingers are good at preserving slots in combat, freeing them to help resolve some of the non-combat challenges (and just last for 8 encounters). Racial choice would be Dragonmarked Halfling (Mark of Healing) in order to put healing spells on my list as backup healer. Criminal background for stealth and backup to rogue.
Druid is probably the most iffy choice between the short rest nerf hitting wildshape, and just needing a lot of slots between combat and non-combat challenges - that's a lot of scenes in the day. So want to focus being a back-line caster with spells like Call Lightening that are very slot efficient.
Using Tasha's to adjust racial ability scores. Pick backgrounds where not listed to get stealth.
One combat plan is to haste the rogue, who will use the haste action to make their one attack, and then their normal action to ready an attack on someone else's turn. Satyr gives magic resistance.
Again, this is a party around a particular gimmick - all flying, stealthy characters - for overcoming a particular format - 8 encounters + non-combat challenges in the other pillars of play. Not a normal campaign party.
That's not really a bad thing.
